Silicon crystallization apparatus and silicon crystallization method thereof

ABSTRACT

A novel silicon crystallization apparatus and a silicon crystallization method renders it is possible to form alignment key without additional photolithography, and to adjust a substrate to a correct position by sensing a deviation of the substrate when the substrate is loaded. The silicon crystallization apparatus includes a moving stage being moved in a horizontal direction, and a fixing plate provided in the moving stage, to fix a substrate. A rotating frame is provided in the moving stage, to rotate the fixing plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims the benefit under 35 U.S.C. §119of Korean Application No. P2003-096578, filed on Dec. 24, 2003, which ishereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a silicon crystallization method and a siliconcrystallization apparatus, in which it is possible to form an alignmentkey without additional photolithography, and to adjust the substrate toa correct the position by sensing a deviation of the substrate when thesubstrate is loaded.

2. Discussion of the Related Art

Various displays increase in demand as information technologies develop.Recently, many efforts have been made to research and develop variousflat display panels such as a liquid crystal display device (LCD), aplasma display panel (PDP), an electroluminescent display (ELD), avacuum fluorescent display (VFD), and the like. Some types of the flatdisplay panels have already been used in various display devices.

LCDs are most widely used because of their beneficial characteristicsand advantages including high quality images, light weight, thin andcompact size, and low power consumption. LCDs can be used as substitutesfor cathode ray tubes (CRT) for mobile image display devices. LCDs havealso been developed for use in devices receiving and displayingbroadcast signals, such as televisions, computer monitors, and the like.

Generally, an LCD device includes an LCD panel for displaying an imageand a driving unit for applying driving signals to the LCD panel. TheLCD panel includes first and second glass substrates bonded to eachother and a liquid crystal layer injected between the first and secondsubstrates.

In this case, on the first glass substrate (TFT array substrate), gatelines are formed to be arranged in one direction at fixed intervals,data lines are arranged perpendicularly to the gate lines at fixedintervals, pixel electrodes are formed in a matrix-type configuration inpixel regions defined by the gate and data lines crossing each other,and thin film transistors are switched by signals of the gate lines totransfer signals from the data lines to the pixel electrodes.

On the second glass substrate (color filter substrate), there is a blackmatrix layer for shielding light from other portions except the pixelregions. On the second glass substrate can also be found an R/G/B(Red/Green/Blue) color filter layer for realizing colors, and a commonelectrode for realizing an image.

The above-described first and second glass substrates are maintained ata predetermined interval from each other by spacers, and the substratesare bonded to each other by a sealant having a liquid crystal injectioninlet. Liquid crystal material is injected between the two glasssubstrates.

The general driving principle of an LCD device uses the opticalanisotropy and polarization characteristics of the liquid crystal.Because the structure of a liquid crystal molecule is thin and long, theliquid crystal molecules are aligned along a specific direction. Basedupon dipole moment, the liquid crystal molecules can have eitherpositive or negative dielectric anisotropy. Applying an induced electricfield to the liquid crystal controls the direction of the alignment.Therefore, when the alignment of the liquid crystal molecules isarbitrarily controlled, the alignment of the liquid crystal moleculeseventually alters. Subsequently, due to the optical anisotropy of liquidcrystals, light rays are refracted in the direction of the alignment ofthe liquid crystal molecules, thereby representing image information.

In recent technologies, an active matrix liquid crystal display (LCD),which is formed of a thin film transistor and pixel electrodes alignedin a matrix form and connected to the thin film transistor, isconsidered to have excellent high resolution and is noted for itsability to represent animated images.

In an LCD device having a polysilicon semiconductor layer of the thinfilm transistor, it is possible to form the thin film transistor and adriving circuit on the same substrate. Also, there is no requirement toconnect the thin film transistor with the driving circuit, whereby thefabrication process is simplified. In addition, the field effectmobility of polysilicon is one to two hundred times higher than thefield effect mobility of amorphous silicon, thereby obtaining a greatstability to temperature and light.

The method of fabricating the polysilicon can be divided into a lowtemperature fabrication process and a high temperature fabricationprocess depending upon the fabrication temperature.

The high temperature fabrication process requires a temperature ofapproximately 1,000° C., which is equal to or higher than thetemperature required for modifying substrates. Glass substrates havepoor heat-resistance, and hence expensive quartz substrates havingexcellent heat-resistance should be used. When fabricating a polysiliconthin film by using the high temperature fabrication process, inadequatecrystallization may occur due to high surface roughness and fine crystalgrains, thereby resulting in poor device characteristics, as compared topolysilicon formed by the low temperature fabrication process.Therefore, technologies for crystallizing amorphous silicon, which canbe vapor-deposited at a low temperature to form polysilicon, have beenresearched and developed.

The method of depositing amorphous silicon at low temperature, andcrystallizing the deposited amorphous silicon, can be categorized as alaser annealing process and a metal induced crystallization process.

The low temperature laser annealing process includes irradiating apulsed laser beam on a substrate. More specifically, by using the pulsedlaser beam, the solidification and condensation of the substrate can berepeated about every 10 to 100 nanoseconds. The low temperaturefabrication process has the advantage that the damage caused on a lowerinsulating substrate can be minimized.

The related art crystallization method of silicon using the laserannealing method will now be explained in detail.

FIG. 1 illustrates a graph showing the size of amorphous siliconparticles versus laser energy density.

FIG. 1 shows that the crystallization of amorphous silicon can bedivided into a first region, a second region, and a third regiondepending upon the intensity of laser energy.

The first region is a partial melting region where the intensity of thelaser energy irradiated on the amorphous silicon layer is sufficient topenetrate only the surface of the amorphous silicon layer. Afterirradiation, the surface of the amorphous silicon layer partially meltsin the first region, and small crystal grains are formed on the surfaceof the amorphous silicon layer after the solidification process.

The second region is a near-to-complete melting region where theintensity of the laser energy, being higher than that of the firstregion, almost completely melts the amorphous silicon. After melting,the remaining nuclei are used as seeds for crystal growth to therebyform crystal particles with an increased crystal growth, as compared tothe first region. However, the crystal particles formed in the secondregion are not uniform. The second region has a narrower laser energydensity band than the first region.

The third region is a complete melting region where laser energy with anincreased intensity, as compared to that of the second region, isirradiated to completely melt the amorphous silicon layer. After thecomplete melting of the amorphous silicon layer, a solidificationprocess is carried out to allow homogenous nucleation, thereby forming acrystal silicon layer formed of fine and uniform crystal particles.

In this method of fabricating polysilicon, the number of laser beamirradiations, i.e., shots, and the degree of overlap are controlled inorder to form uniform, large and rough crystal particles by using theenergy density of the second region.

However, the interfaces between the many polysilicon crystal particlesact as impediments to electric current flow, thereby decreasing thereliability of the thin film transistor device. In addition, collisionsbetween electrons may occur within the many crystal particles to causedamage to the insulating layer due to the collision current anddeterioration, thereby resulting in product degradation or defects. Inorder to resolve such problems, fabricating polysilicon uses asequential lateral solidification (SLS) method, where the crystal growthof the silicon crystal particle occurs at an interface between liquidsilicon and solid silicon in a direction perpendicular to the interface.The related art SLS crystallizing method is disclosed in detail byRobert S. Sposilli, M. A. Crowder, and James S. Im, Mat. Res. Soc. Symp.Proc. Vol. 452, pp. 956-957, 1997.

In the related art SLS method, the amount of laser energy, theirradiation range of the laser beam, and the translation distance arecontrolled to permit lateral growth of a silicon crystal particle with apredetermined length, thereby crystallizing the amorphous silicon into asingle crystal of 1 μm or more.

The irradiation device used for SLS concentrates the laser beam into asmall and narrow region, and the amorphous silicon layer deposited onthe substrate thus cannot be completely converted into polycrystallinesilicon with a single irradiation. Therefore, in order to change theirradiation position on the substrate, the substrate having theamorphous silicon layer deposited thereon is mounted on a stage. Then,after irradiation on a predetermined area, the substrate is moved so asto allow irradiation to be performed on another area, thereby carryingout the irradiation process over the entire surface of the substrate.

FIG. 2 illustrates a schematic view of a related art sequential lateralsolidification (SLS) device. FIG. 2 shows the related art sequentiallateral solidification (SLS) device that includes a laser beam generator1 generating laser beams, a focusing lens 2 focusing the laser beamsdischarged from the laser beam generator 1, and a mask 3 to dividedlyirradiate the laser beam on a substrate 10. A reduction lens 4 formedbelow the mask 3 reduces the laser beam passing through the mask 3 to aconstant width.

The laser beam generator 1 generally produces light with a wavelength ofabout 308 nanometers (nm) using XeCl or a wavelength of 248 nanometers(nm) using KrF in an excimer laser. The laser beam generator 1discharges an unmodified laser beam. The discharged laser beam passesthrough an attenuator (not shown), in which the energy level iscontrolled. The laser beam then passes through the focusing lens 2.

The substrate 10 has an amorphous silicon layer deposited thereon, andthe substrate 10 is fixed on an X-Y stage 5 that faces the mask 3.

In order to crystallize the entire surface of the substrate 10, the X-Ystage 5 is minutely displaced, thereby gradually expanding thecrystallized region.

The mask 3 includes an open part ‘A’ that allows the laser beam to passthrough, and a closed part ‘B’ blocks the laser beam (see FIG. 3). Thewidth of the open part ‘A’ determines the lateral growth length of thegrains formed after the first exposure.

FIG. 3 shows a plane view of a mask used in a laser irradiation process.FIG. 4 shows a crystallized region formed by a laser beam irradiation byusing a mask of FIG. 3. Referring to FIG. 3, the mask used in the laserirradiation process is formed with the open part ‘A’ having patternsopened at a first interval (a), and the closed part ‘B’ has patternsclosed at a second interval (b). The open and closed parts alternatesequentially.

The laser irradiation process using the mask will be described asfollows.

First, the mask 3 is placed over the substrate having an amorphoussilicon layer deposited thereon, and then the first laser beam isirradiated. At this time, the irradiated laser beam passes through themultiple open parts ‘A’ of the mask 3, whereby predetermined portions 22of the amorphous silicon layer corresponding to the open parts ‘A’ aremelted and liquefied, as shown in FIG. 4. In this case, the intensity oflaser energy has a value selected from the complete melting region, sothat the silicon layer irradiated with the laser completely melts.

At this time, by a single laser beam irradiation, the multiple openparts ‘A’ of the mask 3 correspond to one unit area 20 of the substrate,to which the laser beam irradiated, where the unit area 20 has a length‘L’ and a width ‘S’.

After the laser beam irradiation, silicon grains 24 a and 24 b growlaterally from interfaces 21 a and 21 b between the amorphous siliconregion and the completely liquefied silicon region, and the grains growtowards the irradiation region. The lateral growth of the silicon grains24 a and 24 b proceeds in a perpendicular direction to the interfaces 21a and 21 b.

In the predetermined portion 22 irradiated with laser corresponding tothe open part ‘A’ of the mask, if the width of the predetermined portion22 is narrower than two times the growth length of the silicon grains 24a, then the grains growing inward in a perpendicular direction from bothsides of the interface of the silicon region come into contact with oneanother at a grain boundary 25, thereby causing the crystal growth tostop.

Subsequently, in order to further grow the silicon grains, the stagebearing the substrate is moved to perform another irradiation process onan area adjacent to the first irradiated area. Another crystal thusforms with the new crystal being connected to the crystal formed afterthe first exposure. Similarly, crystals are laterally formed on eachside of the completely solidified regions. Generally, the crystal lengthproduced by the laser irradiation process and connected to the adjacentirradiated part is determined by the width of open part ‘A’ and closedpart ‘B’ of the mask.

FIG. 5 illustrates an overlapped portion after completing thecrystallization process over the entire surface of the substrate byusing the mask of FIG. 3.

FIG. 5 shows that on progressing the crystallization by the unit areas(C1, C2, . . . , Cm, Cm+1, . . . ) of the substrate irradiated withshots of the laser beam, there are overlapped portions (01, 02) of laserbeam irradiation on the substrate. That is, when irradiating the laserbeam at the adjacent unit areas, the predetermined portions between theadjacent unit areas may be irradiated with the laser beam two (or more)times according to the open part ‘A’ of the mask that partially overlapsthe adjacent unit area. For example, the laser beam irradiates in acondition where the substrate is moved along the X-axis direction at adistance corresponding to the length ‘L’ of the open part of the mask 3,and thus an overlapped portion 01 generates. Also, the laser beamirradiates under the condition where the substrate is moved along theY-axis direction at the distance corresponding to (a+b)/2 of the mask 3,and thus an overlapped portion 02 generates. Among the overlappedportions 01 and 02, there are the overlapped portions 51 and 52 that aretwice irradiated with the laser beam along any one direction of theX-axis or the Y-axis. Also, the overlapped portion 53 is irradiated withthe laser beam four times along the X-axis and the Y-axis directions.

If circuit or display components are positioned in the overlappedportions 51, 52, and 53, the electron mobility may decrease due tonon-uniformity of grains generated during the silicon crystallizationprocess. Also, the picture quality degrades when the overlapped portions51, 52, and 53 are in correspondence with the pixel region of displayarea.

Accordingly, the related art silicon crystallization method has thefollowing disadvantages.

The related art silicon crystallization is performed over the entiresurface of the substrate, and the silicon crystallization processproceeds without an additional alignment key. As a result, it isdifficult to control the position of laser beam overlapped portions.Accordingly, if the laser beam overlapped portions correspond to thepixel regions or a channel region, it may cause deleterious low picturequality and low operation speed.

Generally, an LCD device is defined as the display area and anon-display area. Also, the predetermined portion of the LCD devicerequiring silicon crystallization corresponds to the portion havingcomponents necessary for rapid operating speed. That is, the portionrequiring the silicon crystallization bears the components such as thedisplay area for the driving circuit part (gate driver and data driver),and the non-display area is for the thin film transistor. Accordingly,it is possible to selectively perform the silicon crystallizationprocess to a predetermined portion without applying the siliconcrystallization process over the entire surface of the substrate. Withthe selective silicon crystallization, it is possible to decrease thetime and number of laser irradiations. However, for selective siliconcrystallization, it becomes necessary to provide an alignment key forsensing the portion of the substrate irradiated with the laser beam. Forthis, there arises a requirement to perform photolithography to form theadditional alignment key, thereby placing a burden on the siliconcrystallization process.

SUMMARY OF THE INVENTION

Accordingly, the invention pertains to a silicon crystallizationapparatus and a silicon crystallization method that substantiallyobviates one or more problems due to limitations and disadvantages ofthe related art.

An object of the invention is to provide a silicon crystallizationapparatus and a silicon crystallization method thereof, in which it ispossible to form an alignment key without additional photolithography,and to adjust the substrate to a correct position by sensing thedeviation of the substrate when the substrate is loaded.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, theinvention, in part pertains to a stage for crystallization that includesa moving stage being moved in a horizontal direction; a fixing plateprovided in the moving stage to fix a substrate; and a rotating frameprovided in the moving stage, to rotate the fixing plate.

The stage for crystallization can further include multiple adsorptionpins provided in the fixing plate, for being moved up and down; and avacuum groove formed in a surface of the fixing plate, so as to adsorbthe substrate. The vacuum groove can have a lattice shape.

Also, when the substrate is loaded, the adsorption pins project abovethe fixing plate so as to fix the substrate, and then the fixing plateis moved down while fixing the substrate, so that the substrate isloaded to the surface of the fixing plate.

Further, when the substrate is unloaded, the adsorption pins projectabove the fixing plate, so that the substrate is spaced apart from thefixing plate.

The invention, in part, pertains to a silicon crystallization apparatusthat includes a stage for fixing a substrate having silicon depositedthereon, and for being rotatably and/or movably provided with thesubstrate in a horizontal direction, a sensing device for sensing thesubstrate fixed to the stage and controlling the movement of the stageto align the substrate, and an optical device, i.e., optics, forcrystallizing the silicon by irradiating laser beams onto the substrate.

In the invention, the optical device includes a laser beam generator togenerate laser beams, a focusing lens to focus the laser beams, a maskto dividedly irradiate the focused laser beams onto the substrate whenforming alignment keys, a crystallization mask to selectively irradiatethe focused laser beams onto the substrate when performing acrystallization process, and a reduction lens to reduce the laser beamspassing through the mask to form of the alignment keys and thecrystallization mask.

In the invention, the stage can include a moving stage for being movedin a horizontal direction, a fixing plate provided in the moving stageso as to fix the substrate, a rotating frame provided in the movingstage so as to rotate the fixing plate, multiple adsorption pinsprovided in the fixing plate for being moved up and down, and a vacuumgroove provided in the surface of the fixing plate.

Also, the sensing device senses the corner coordinates of the substrate.The sensing devices include at least first, second, and third sensors.The first and second sensors can be positioned to correspond with thetwo corner coordinates of the long length-side direction of thesubstrate, and the third sensor is positioned to correspondence with thecorner coordinates of the short width-side direction of the substrate.The first, second, and third sensors can be formed of CCD cameras, orthe first, second, and third sensors can bee formed of LD sensors.

The invention, in part, pertains to a silicon crystallization methodthat includes providing a silicon crystallization apparatus includingoptics, i.e., an optical device, for generating laser beams, a stage forfixing a substrate having silicon deposited thereon, the stage beingrotatably and movably provided with the substrate in a horizontaldirection, and a sensing device for sensing the position of thesubstrate. The method also includes forming an amorphous silicon layerover an entire surface of the substrate defined as a display area and anon-display area, fixing the substrate to the stage, aligning thesubstrate by sensing the substrate fixed on the stage with the sensingmeans, and moving and rotating the stage, forming alignment keys onpredetermined portions of the non-display area of the substrate bycorrespondingly placing a mask for formation of alignment keys above thesubstrate, and crystallizing the amorphous silicon by correspondinglyplacing a mask for crystallization above the substrate.

In the invention, the process of aligning the substrate includespositioning first and second sensors to correspond with the cornercoordinates of a length-side direction of the substrate, and positioninga third sensor to correspond with the corner coordinates of a width-sidedirection of the substrate, according to the size of the substrate. Themethod also includes detecting the corner coordinates of the substratewith the first, second, and third sensors, and moving the stage alongthe X-axis and the Y-axis directions, and/or rotating the stage, so asto detect the corner coordinates of the substrate from all of the first,second, and third sensors.

In the invention, the method of moving the stage along the X-axis andthe Y-axis directions, and of rotating the stage, can also include stepsof minutely moving the stage along the (+)(−)X-axis direction so as tosense the corner coordinates of the substrate from the third sensor, ifthe corner coordinates of the substrate are detected from the first andsecond sensors, and not detected from the third sensor. Then, the methodminutely moves the stage along the (+)(−)Y-axis direction so as to sensethe corner coordinates of the substrate from the first and secondsensors, if the corner coordinates of the substrate are detected fromthe third sensor, and not detected from the first and second sensors.Afterwards, the method rotates the stage so as to sense the cornercoordinates of the substrate from both the first and second sensors, andmoves the stage along the (+)(−)X-axis direction so as to sense thecorner coordinates of the substrate from the third sensor, if the cornercoordinates are detected from any one of the first and second sensors.

In a preferred embodiment, the alignment key is formed in shape of ‘

’. Also, when forming the alignment keys, the laser beam is irradiatedat a first energy density at an intensity suitable for ablating theamorphous silicon layer. When performing the crystallization process,the laser beams is irradiated at a second energy density at an intensitysufficient to completely melt the amorphous silicon layer.

In the invention, the process of crystallizing the amorphous siliconlayer is performed using a first step of selectively crystallizingpredetermined portions of the display area, and a second step ofcrystallizing a driving circuit part of the non-display area.

The invention, in part, pertains to a silicon crystallization methodthat includes providing a silicon crystallization apparatus includingoptical means for generating laser beams, a stage for fixing a substratehaving silicon deposited thereon, and for being rotatably and movablyprovided with the substrate in a horizontal direction, and a sensingdevice for sensing the position of the substrate. The method includessteps of forming an amorphous silicon layer over an entire surface ofthe substrate defined as a display area and a non-display area, fixingthe substrate to the stage, aligning the substrate by sensing thesubstrate fixed on the stage with the sensing means, and moving androtating the stage. The method further includes forming alignment keyson predetermined portions of the non-display area by correspondinglyproviding a mask for formation of alignment key above the substrate,crystallizing the amorphous silicon on predetermined portions of thedisplay area by correspondingly placing a first crystallization maskabove the substrate, and crystallizing the amorphous silicon of thenon-display area by correspondingly placing a second crystallizationmask above the substrate.

In the invention, the process of crystallizing the amorphous siliconwith the first crystallization mask is performed while sensing aninterval between the alignment key and the predetermined portion of thesubstrate irradiated with the laser beams. Also, the firstcrystallization mask contains an open part and a closed part, and alength and a width in the open part of the first crystallization maskare controlled according to a size of a semiconductor layer in eachpixel. The first crystallization mask can include at least one patternblock corresponding to a semiconductor layer part in each pixel.Further, the process of crystallizing the amorphous silicon with thesecond crystallization mask is performed while sensing an intervalbetween the alignment key and the predetermined portion of the substrateirradiated with the laser beams.

It is to be understood that both the foregoing general description andthe following detailed description of the invention are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings;

FIG. 1 illustrates a graph showing the size of amorphous siliconparticles versus laser energy density;

FIG. 2 illustrates a schematic view of a related art laser irradiationapparatus for a general SLS method;

FIG. 3 illustrates a plane view of a related art mask used in a laserirradiation process;

FIG. 4 illustrates a crystallized area formed by a first laser beamirradiation with a mask of FIG. 3;

FIG. 5 illustrates a laser beam overlapped portion formed on apredetermined area after performing a crystallization process over anentire surface of a substrate;

FIG. 6 illustrates a plane view of respective regions formed on asubstrate according to the invention;

FIG. 7 illustrates an expanded plane view of an alignment key of FIG. 6according to the invention;

FIG. 8 illustrates a cross sectional view of an alignment key along I-I′of FIG. 7 according to the invention;

FIG. 9 illustrates a perspective view of a stage for a crystallizationprocess according to the invention;

FIG. 10 illustrates a plane view of a substrate loaded on a correctposition of a stage according to the invention;

FIG. 10 illustrates a plane view of a case for loading a substratedeviated from a fixation plate according to the invention;

FIG. 12A and FIG. 12B illustrate plane views of a case a substrateslides on a fixing plate according to the invention;

FIG. 13 illustrates a perspective view of a silicon crystallizationapparatus according to the first embodiment of the invention; and

FIG. 14A to FIG. 14D illustrate a silicon crystallization process with asilicon crystallization apparatus of FIG. 13 according to the invention.

FIG. 15 shows a silicon crystallization apparatus using a laser diodesensor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Hereinafter, a silicon crystallization apparatus and a siliconcrystallization method according to the invention will be described withreference to the accompanying drawings.

FIG. 6 illustrates a plane view of respective regions formed on asubstrate according to the invention. FIG. 6 shows a substrate 100 for athin film transistor array of an LCD device is defined as a display area110 for displaying a substantial image, and a non-display area 120surrounds the display area 110. An amorphous silicon layer is depositedover the entire surface of the substrate 100.

On the display area 110, multiple gate and data lines (not shown,positioned in portions except pixel regions of the display area)crossing each other are formed to define the pixel regions 125, and apixel electrode is formed in each of the pixel regions 125. Also, a thinfilm transistor is formed at a crossing portion of the gate and datalines in a predetermined portion of the pixel region 125, where the thinfilm transistor is formed from a gate electrode (not shown) protrudingfrom the gate line, a source electrode (not shown) protruding from thedata line, and a drain electrode (not shown) provided at a predeterminedinterval from the source electrode. In addition, a semiconductor layer127 is formed below the source electrode and the drain electrode so asto form a channel between them.

A driving circuit part of a gate driver 140 and a source driver 150 isformed over the non-display area 120 so as to apply signals to therespective gate and data lines of the display area 110.

Also, an alignment key 130 is formed over the substrate 100. Thealignment key 130 is used for patterning crystalline silicon in thesemiconductor layer, or for sensing an exposure area of the substrate byphotolithography to form the gate line, the data line, or the pixelelectrode.

This alignment key 130 may be additionally formed by photolithography.However, the inventive silicon crystallization method can have thealignment key 130 being formed by irradiating a laser beam at eachcorner of the non-display area 120 at an energy density suitable forablation of the amorphous silicon layer during the siliconcrystallization process. In this case, the alignment key 130 formedduring the silicon crystallization process may be used several times forthe following photolithography.

FIG. 7 illustrates an expanded plane view of the alignment key of FIG. 6according to the invention. FIG. 8 illustrates a cross sectional view ofthe alignment key along I-I′ of FIG. 7 according to the invention.

As shown in FIG. 7 and FIG. 8, the alignment key 130 is formed with amask (not shown), the mask for formation of the alignment key preferablyhaving a shape of

The alignment key is not restricted to the shape of

and other appropriate shapes can be used. These shapes can include butare not restricted to

‘+’, ‘⋄’,

‘□’, ‘→’, or ‘∘’.

The energy density of laser beam is about at the intensity (or greater)of completely melting the amorphous silicon layer, and of removing theamorphous silicon layer irradiated with the laser beam by ablation. Inthis laser beam irradiation process, the alignment key 130 is definednot by completely removing an amorphous silicon layer of the preferred

-shaped pattern, but by removing a plurality of minute patterns 135having a critical dimension (CD) down to about 0.1 μm or smaller in the

-shaped pattern.

Unlike the related art photolithography that removes or leaves a desiredregion by using a photosensitive pattern (photoresist pattern), theinventive alignment keys can be patterned by depositing a buffer layer104 and the amorphous silicon layer 106 over an entire surface of thesubstrate 102, volatilizing a predetermined portion of the amorphoussilicon layer 106 by increasing the intensity of laser beam irradiation,forming multiple minute patterns 131 in intaglio, and defining thealignment key 130 of

shape with the plurality of minute patterns 131 (see FIG. 8). At thistime, the alignment key 130 may be formed in shape of

‘+’, ‘⋄’,

,

‘□’, ‘→’, or ‘∘’by changing the pattern of the mask for forming thealignment key. However, the alignment key is not restricted to theseshapes, and any appropriate shape can be used.

FIG. 9 illustrates a perspective view of a stage in a siliconcrystallization apparatus for crystallizing amorphous silicon accordingto the invention. FIG. 9 shows a stage 160 of a silicon crystallizationapparatus for crystallizing amorphous silicon that is provided with amoving stage 200, a fixing plate 220, pins 230, a rotating frame 250,and a vacuum groove 225. The moving stage 200 moves a loaded substrate(not shown) in all directions, and the fixing plate 220 fixes the loadedsubstrate (not shown). Also, the pins 230 are provided at corners of thefixing plate 220, and the pins 230 are moved upward and downward so asto adsorb the loaded substrate. The rotating frame 250 rotates thefixing plate 220 to adjust the loaded substrate to a correct positionwithout deviation or sliding. The vacuum groove 225 is provided on thesurface of the fixing plate 220 to fix the substrate to the fixing plate220 without leaving any gap.

When the substrate is loaded on the fixing plate 220, the pins 230project above the fixing plate 220 to fix the loaded substrate. Then,the pins 230 move downward to adsorb the loaded substrate, so that theloaded substrate is fixed to the surface of the fixing plate 220. Inthis case, the vacuum groove 225 uniformly formed on the surface of thefixing plate 220 adsorbs the loaded substrate with the pins 230 by usinga vacuum, and the loaded substrate is thus fixed to the surface of thefixing plate 220 without a gap. The vacuum groove 225 is preferablyformed in a lattice shape.

When loading the substrate to the stage 160, the substrate may deviateor slide, so that the substrate may not be positioned at the correctcorresponding position of the stage 160. To correct this problem, thestage 160 has the rotating frame 250 for adjusting the substrate in casethe substrate deviates or slides, so that it is possible to adjust theloaded substrate by minutely rotating or moving the fixing plate 220 atall directions.

Due to the spatial limitations in advancing the crystallization process,the laser beam irradiation area by the mask pattern corresponds to thepredetermined portion of the substrate, whereby the moving stage 200moves the stage 160 bearing the substrate in one direction. Alternately,rotating the stage 160 bearing the substrate at an angle of 90°progresses the crystallization process. In this case, the moving stage200 may move the stage 160 along both the X-axis and Y-axis directions.

FIG. 10 illustrates a plane view of the substrate correctly loaded onthe desired position of the stage. FIG. 10 shows that if the substrate100 is loaded at the correct portion of the fixing plate 220 of thestage 160, the alignment keys 130 formed in four corners of thesubstrate 100 correspond with the portions V for the pins formed at fourcorners of the stage.

However, when loading the substrate 100 on the fixing plate 220, thesubstrate 100 may generally deviate or slide. Accordingly, the alignmentkeys 130 formed in four corners of the substrate 100 may not correspondwith the portions V for the pins formed in four corners of the stage.

A case adjusting the substrate loaded to the fixing plate will bedescribed with reference to the accompanying drawings.

FIG. 11 illustrates a plane view of a case for loading the substratedeviated from the fixing plate according to the invention. FIG. 12A andFIG. 12B illustrate plane views of the situation where the substrateslides on the fixing plate according to the invention.

FIG. 11 shows that when the substrate 100 is externally loaded on thefixing plate 220 of the stage, the substrate 100 may deviate from thecorrect position of the fixing plate due to the external force.

Also, as shown in FIG. 12A and FIG. 12B, when the substrate 100 isexternally loaded on the fixing plate 220, the substrate 100 istransferred to the fixing plate 220 by a robot arm. In this case, thesubstrate 100 may not stop at the correct position on the fixing platedue to the speed, and thus the four corners of the substrate 100 may notbe positioned to correspond with the portions V for the pins. That is,the substrate 100 may slide relative to the correct area of the fixingplate 220. FIG. 12A illustrates the situation where the substrate slidesdown toward the right side relative to the portions V for the pins ofthe stage. FIG. 12B illustrates the situation where the substrate slidesup toward the left side relative to the portions V for the pins of thestage.

In the cases of FIG. 11, FIG. 12A, and FIG. 12B, there are requirementsfor rotating the fixing plate in a clockwise direction, or moving thestage to the northwest or southeast (i.e., diagonal) direction tothereby aligning the substrate. Especially, for the inventive siliconcrystallization method, the crystallization process is selectivelyperformed at predetermined portions of the substrate instead of over theentire surface of the substrate. In this respect, it becomes necessaryto sense the deviation or the sliding of the substrate, and to adjustthe substrate to the correct position. As a result, the crystallizationprocess is correctly performed at selected portions of the substrate.

A silicon crystallization apparatus having additional position sensorsabove the stage will be described as follows.

FIG. 13 illustrates a perspective view of a silicon crystallizationapparatus according to the first embodiment of the invention. FIG. 13shows a silicon crystallization apparatus that is provided with optics(not shown), a fixing plate 220 and adsorption pins 230 of a stage 160,a sensing device 300, and an adjusting mechanism 250. At this time, theoptics (not shown) irradiates a laser beam to predetermined patterns ofa substrate. Then, the substrate is loaded on the stage 160 by thefixing plate 220 and the adsorption pins 230 using vacuum adsorption.Also, the sensing device 300 is provided to sense the position of thesubstrate loaded to the fixing plate 220, and the adjusting mechanism250 adjusts the substrate deviated from or sliding on the fixing plate220. As explained above, the adjusting mechanism is preferably formedfrom a rotating frame 250.

The optics is provided with a laser beam generator for irradiating alaser beam, a condensing lens for condensing the laser beam, a mask forforming alignment keys to correspond with selected portions, a mask fora crystallization process, and a reducing lens for reducing the laserbeam transmitted by the masks for the alignment keys and crystallizationprocess. The optics thus transmit laser beam patterns. The optics areprovided above the stage 160 when loading the substrate 100, so as toirradiate the laser beam at the corresponding patterns of the substrate100 by using the mask for making the alignment keys or the mask for thecrystallization process.

The stage of FIG. 13 has the same structure as that of FIG. 9.

Here, the adsorption pins 230 move up and down. That is, when thesubstrate 100 is loaded to the fixing plate 220 by a loader (not shown),the adsorption pins 230 move up to fix the substrate. When the loaderunloads the substrate, the adsorption pins 230 move down so as to movethe substrate downward, whereby the substrate is loaded on the surfaceof the fixing plate 220. After that, the substrate is fixed using alattice-shaped vacuum groove 225 formed on the surface of the fixingplate 220.

The sensing device 300 senses the position of the substrate 100 so as toadjust the position of the deviated substrate by minutely moving therotating frame 250, or to adjust the position of the slid substrate bymoving the stage. The sensing device 300 may be a CCD (charge coupleddevice) camera or an LD (laser displacement) sensor. That is, three (ormore) CCD cameras or LD sensors are provided in correspondence with thecorners (or edges) of the substrate fixed to the fixing plate 220. Thesensing device 300 is provided in the optics, and the sensing device 300is perpendicular at a predetermined interval from the substrate 100.Also, each of the first, second, and third sensors 301, 302, and 303 ofthe sensing device 300 is provided at the same distance from thesubstrate 100. If using CCD cameras as the sensing device 300, the CCDcameras map the corners of the substrate. If using LD sensors as thesensing device 300, the LD sensors sense the step difference of thecorners of the substrate using a laser scanning method.

FIG. 13 shows that the sensing device 300 is provided with the first,second, and third sensors 301, 302, and 303 (three CCD cameras or threeLD sensors). The first and second sensors 301 and 302 are positioned tocorrespond with the two corners of the longer length-side direction ofthe substrate, and the third sensor 303 is positioned to correspond withone corner of the short width-side direction of the substrate. Thesubstrate has a rectangular shape so that it is possible to sense theposition of the substrate with the three CCD cameras or the three LDsensors.

The inventive silicon crystallization apparatus has the substrate beingfixed to the fixing plate 220 by the adsorption pins 230 and the vacuumgroove 225, and the position of the substrate is sensed with the sensingdevice 300. If the substrate deviates from the correct position, therotating frame 250 operates to adjust the substrate. Also, if thesubstrate slides, the stage is moved along the X-axis and the Y-axisdirection so as to adjust the substrate.

FIG. 14A to FIG. 14D illustrate the inventive silicon crystallizationprocess using the silicon crystallization apparatus of FIG. 13.

First, the substrate 100 (which is defined into a display area and anon-display area) is prepared, and an amorphous silicon layer is formedover the entire surface of the substrate 100.

FIG. 14A shows that the substrate 100 is moved to the fixing plate 220of the stage 160 by the loader 180. Then, as shown in FIG. 14B, when thesubstrate 100 is positioned above the fixing plate 220, the adsorptionpins 230 move up to adsorb, i.e., support, the substrate 100, and thenthe loader 180 is retracted.

Afterwards, the adsorption pins 230 move down while supporting thesubstrate 100, so that the substrate 100 is loaded on the surface of thefixing plate 220. Then, the loaded substrate 100 is fixed to the fixingplate 220 using the vacuum groove 225.

FIG. 14C shows the sensing device 300 sensing the position of thesubstrate 100 fixed to the fixing plate 220, so that it is possible tosense whether the substrate 100 deviates or slides from the correctposition. That is, the first and second sensors 301 and 302 (two CCDcameras or two LD sensors) are provided to correspond with the twocorners of the long length-side direction of the substrate, and thethird sensor 303 (one CCD camera or one LD sensor) is provided tocorresponds with one corner of the short width-side direction of thesubstrate. After fixing the substrate to the fixing plate 220, thesubstrate is checked to determine whether the corner coordinates aredetected by the first, second, and third sensors 301, 302, and 303.

FIG. 15 shows a variation of the configuration of FIG. 14C where thesensing device 300 senses the position of the substrate 100 fixed to thefixing plate 220, so that it is possible to sense whether the substrate100 deviates or slides from the correct position. In this embodiment,the laser diode (LD) sensing device 310 has first and second sensors 311and 312 (two LD sensors) are provided to correspond with the two cornersof the long length-side direction of the substrate, and the third sensor313 (one LD sensor) is provided to correspond with one corner of theshort width-side direction of the substrate. After fixing the substrateto the fixing plate 220, the substrate is checked to determine whetherthe corner coordinates are detected by the first, second, and third LDsensors 311, 312, and 313.

If the corner coordinates of the substrate are sensed by the threesensors, the substrate is re-aligned with the sensed corner coordinates,thereby correctly aligning the substrate. That is, even if the cornercoordinates of the substrate are detected, the substrate is re-alignedto the correct position. Also, if the corner coordinates of thesubstrate are not detected by all three sensors, the coordinates aredetermined as the substrate deviates or slides. The moving stage 200 isaccordingly moved along the X-axis direction and the Y-axis direction,so that the corner coordinates of the substrate are detected by all thethree sensors.

If the first and second sensors 301 and 302 provided in the longlength-side direction of the substrate sense the corner coordinates ofthe substrate, and if the third sensor 303 provided in the shortwidth-side direction of the substrate doesn't sense the cornercoordinates of the substrate, then the moving stage 200 is minutelymoved along the (+)(−) X-axis direction so that the third sensor 303senses the corner coordinates of the substrate.

Also, if the corner coordinates of the substrate are sensed only by thethird sensor 303 provided in the short width-side direction of thesubstrate, and if the corner coordinates of the substrate are not sensedby the first and second sensors 301 and 302 provided in the longlength-side direction of the substrate, then the moving stage isminutely moved along the (+)(−) Y-axis direction so that the first andsecond sensors 301 and 302 sense the corner coordinates of thesubstrate.

By moving the moving stage 200, the corner coordinates are sensed by anyone of the first and second sensors 301 and 302, and it is determined ifthe substrate deviates from the correct position. In this situation, therotating frame 250 operates so that the corner coordinates of thesubstrate are sensed in both the first and second sensors 301 and 302,thereby adjusting the substrate to the correct position. Also, by movingthe moving stage 200, the corner coordinates of the substrate are sensedby the third sensor 303.

After aligning the substrate fixed to the fixing plate 220, the mask(not shown) for forming the alignment keys is positioned above thesubstrate 100. The alignment key pattern is preferably formed in shapeof ‘

’.

Subsequently, as shown in FIG. 14D, the laser beam is irradiated at afirst energy density at predetermined portions of the non-display areathrough the mask for forming the alignment keys, thereby forming thealignment keys 130. The alignment keys 130 correspond with the comers ofthe substrate 100. In this case, the substrate is pre-aligned accordingto the process discussed above, and then the substrate is placed at thecorrect position by using the alignment keys 130.

At this time, the first energy density of laser beam is adjusted to theintensity of completely ablating the amorphous silicon layer. That is,the laser beam irradiates at the energy density required to completelymelt the amorphous silicon layer (third region of FIG. 1), so that theamorphous silicon layer of the substrate 100 corresponding to thepreferred ‘

’-shaped pattern of the mask is not crystallized, so as to be ablated asa number of minute patterns having a critical dimension CD down to about1 μm or smaller.

Subsequently, the mask (not shown) for the silicon crystallizationprocess is positioned above the substrate 100. Then, the laser beam isirradiated at a second energy density at the substrate 100 through themask, thereby performing the crystallization process. In this case, thesilicon crystallization process using the mask may be entirely performedon the substrate without division. Alternately, the siliconcrystallization process may be selectively performed on the substrate bythe sequential process of crystallizing the semiconductor layer of thedisplay area (‘127’ of FIG. 6), and by crystallizing the driving circuitpart of the non-display area.

In the latter case of the selective silicon crystallization process, theinterval between the laser beam irradiation portion of the substrate 100and the alignment key 130 is sensed with the alignment keys 130 formedat the corners of the substrate 100.

In both the entire and selective silicon crystallization process, thealignment keys 130 are formed before the crystallization process, andthe alignment keys are used for a patterning process proceeding afterthe crystallization process.

The second energy density is set at the energy density (third region ofFIG. 1) necessary to completely melt the amorphous silicon layer, so asto be suitable for SLS (sequential lateral solidification).

Although not shown, the mask for the silicon crystallization process isprovided with alternately formed open parts and closed parts.

For the latter case of the selective silicon crystallization process,the length and width of the mask for the silicon crystallization processis controlled in accordance with the size of the semiconductor layer ofthe pixel regions formed on the substrate. The length and width of thesemiconductor layer formed on the pixel regions are within several tensof μm, whereby the open part of the mask has a smaller length than thatof a general mask for the crystallization process.

If the crystallization process is performed on the semiconductor layerpart of the display area and the driving circuit part of the non-displayarea by using one mask for the crystallization process, then the numberof laser irradiations required for crystallizing the driving circuitpart increases because the open part of the mask has a small size.Accordingly, in addition to the mask for the crystallization process tothe display area, there is a requirement for providing a mask having alonger open part, thereby simplifying the laser beam irradiationprocess.

Both the first energy density for the alignment keys and the secondenergy density for the crystallization process are set at the energydensity corresponding to the third region of FIG. 1. However, the slitwidth (about 10 μm) of the mask for the alignment keys is relativelylarger than the slit width (about 2-3 μm) of the mask for thecrystallization process. In this respect, even though the laser beamhaving the same energy is irradiated, the irradiated magnitude of thelaser beam for forming the alignment keys is usually greater than theirradiation magnitude of the laser beam used for the crystallizationprocess.

After completing the crystallization process, the adsorption force ofthe fixing plate 220 is removed, and the adsorption pins 230 move up,whereby the substrate 100 moves apart from the fixing plate 220. Then,as explained above, the loader 180 is positioned between the substrate100 and the fixing plate 220, and the crystallized substrate isunloaded.

Another crystallizing method will be described as follows.

First, a substrate defined into a display area and a non-display area isprepared, and an amorphous silicon layer is formed over the entiresurface of the substrate.

As shown in FIG. 14A, the substrate 100 is positioned above the fixingplate 220 of the stage 160. Then, as shown in FIG. 14B, the substrate100 is fixed to the fixing plate 220 by using the adsorption pins 230and the vacuum groove 225. After that, as shown in FIG. 14C, the cornercoordinates of the substrate are sensed with the sensing device 300.According to the sensing results, the moving stage 200 is moved alongthe X-axis direction and the Y-axis direction, and the rotating frame250 is operated to align the substrate, whereby the deviated or slidsubstrate is aligned.

Subsequently, the mask (not shown) for forming the alignment keys iscorrespondingly placed above the substrate 100. Then, as shown in FIG.14D, the laser beam irradiates at a first energy density toward thepredetermined portions of the non-display area through the mask forforming the alignment keys, thereby forming the alignment keys 130.

Then, the first crystallization mask (not shown) is correspondinglyprovided above the substrate. After that, the laser beam irradiates at asecond energy density toward the predetermined portion of the displayarea through the first crystallization mask. At this time, during thecrystallization process using the first crystallization mask, the laserbeam is irradiates while sensing the interval between the predeterminedportions of the substrate irradiated with laser beam and the alignmentkeys.

The predetermined portions of the display area corresponding to thefirst crystallization mask are formed from the semiconductor layer part.

The first crystallization mask has at least one pattern blockcorresponding to the semiconductor layer part. That is, when the firstcrystallization mask has multiple pattern blocks corresponding to thesemiconductor layer part, the pattern blocks of the firstcrystallization mask are provided to have the laser beam irradiationportions being spaced in correspondence with the pixel intervals. Thisspacing is in due consideration of the reducing ratio of the firstcrystallization mask to the substrate 100. The pattern blocks have thecorresponding size of the semiconductor layer part, wherein multipleopen and closed parts are alternately provided.

In the pattern blocks of the first crystallization mask, the length andwidth of the first crystallization mask is controlled in accordance withthe size of the semiconductor layer of the pixel regions formed on thesubstrate. Usually, the length and width of the semiconductor layerformed on the pixel regions are within several tens of μm, whereby theopen part of the mask has a smaller length than that of the general maskused for the crystallization process.

Subsequently, the second crystallization mask is placed above thesubstrate. The second crystallization mask also has multiple alternateopen and closed parts. At this time, the open part has a width ofseveral tens of μm, and the open part has a length of about several mmto several thousand mm.

Afterwards, the laser beam irradiates at a second energy density towardthe driving circuit part of the non-display area through the secondcrystallization mask. The laser beam irradiates while sensing theinterval between the predetermined portions of the substrate irradiatedwith laser beam and the alignment keys. In this case, it is unnecessaryto check the interval between the alignment keys 130 and the laser beamirradiated portions of the substrate whenever the laser beam isirradiated. That is, the interval between the alignment keys and thesubstrate irradiated with the laser beam is checked at the start pointand the end point of the laser beam irradiated in one direction.

This crystallization method uses the same process as that of the formercrystallization method, except that this crystallization methodseparately performs the crystallization process for the semiconductorlayer part of the display area and the driving circuit part of thenon-display area using the two masks.

After completing the crystallization process, the adsorption force ofthe fixing plate 220 is removed, and the adsorption pins 130 move up,whereby the substrate 100 moves apart from the fixing plate 220. Then,as explained above, the loader 180 is positioned between the substrate100 and the fixing plate 220, and the crystallized substrate is removed.

Accordingly, the silicon crystallization apparatus and the siliconcrystallization method of the invention have the following advantages.

In the inventive silicon crystallization apparatus, the sensing deviceis provided to determine whether the substrate deviates or slides. Afterdetermining the position of the substrate, the substrate is aligned bymoving the stage or operating the rotating frame, whereby the alignmentkeys are formed at the correct positions.

Without the additional photolithography, a laser beam having high energydensity is irradiated through the mask to form the alignment keys beforeperforming the crystallization process, thereby forming the alignmentkeys by ablating predetermined portions of the amorphous silicon layer.The alignment keys may be used for all the processes entailingpatterning after the crystallization process, without an additionalprocess for forming the alignment keys.

Also, since the alignment keys are formed after pre-aligning, thealignment keys are easily recognizable in an exposure apparatus.

Furthermore, even though the different substrates are loaded, it becomespossible to form the alignment keys at the same position in eachsubstrate. Accordingly, if there is a requirement to selectivelycrystallize the divided areas, it becomes possible to selectivelyperform the crystallization process on the substrate with the alignmentkeys, in due consideration of the interval.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the invention covers the modifications and variations ofthis invention provided they come within the scope of the appendedclaims and their equivalents.

1. A stage for crystallization comprising: a moving stage that can movein a horizontal direction; a fixing plate provided in the moving stage,the fixing plate for fixing a substrate; and a rotating frame providedin the moving stage, the rotating frame for rotating the fixing plate.2. The stage for crystallization of claim 1, further comprising: aplurality of adsorption pins provided in the fixing plate, theadsorption pins capable of being moved up and down; and a vacuum grooveformed in a surface of the fixing plate, the vacuum groove capable ofadsorbing the substrate.
 3. The stage for crystallization of claim 2,wherein, when the substrate is loaded, the adsorption pins areprojecting above the fixing plate so as to fix the substrate, and thenthe fixing plate is moved down while fixing the substrate, so that thesubstrate is loaded onto the surface of the fixing plate.
 4. The stagefor crystallization of claim 2, wherein, when the substrate is unloaded,the adsorption pins are projecting above the fixing plate, so that thesubstrate is spaced apart from the fixing plate.
 5. The stage forcrystallization of claim 2, wherein the vacuum groove has a latticeshape.
 6. A silicon crystallization apparatus comprising: a stage forfixing a substrate having silicon deposited thereon, the stage beingrotatably and movably provided with the substrate in a horizontaldirection; a sensing device for sensing the substrate fixed to thestage, and controlling the movement of the stage to align the substrate;and an optical device for crystallizing the silicon by irradiating laserbeams to the substrate.
 7. The silicon crystallization apparatus ofclaim 6, wherein the optical device includes: a laser beam generator; afocusing lens to focus the laser beams; a mask to dividedly irradiatethe focused laser beams onto the substrate when forming alignment keys;a crystallization mask to selectively irradiate the focused laser beamsonto the substrate when performing a crystallization process; and areduction lens to reduce the laser beams passing through the mask forformation of the alignment keys and the crystallization mask.
 8. Thesilicon crystallization apparatus of claim 6, wherein the stageincludes: a moving stage for moving in a horizontal direction; a fixingplate provided in the moving stage so as to fix the substrate; and arotating frame provided in the moving stage so as to rotate the fixingplate.
 9. The silicon crystallization apparatus of claim 8, furthercomprising: a plurality of adsorption pins provided in the fixing plate,the adsorption pins capable of being moved up and down; and a vacuumgroove provided in the surface of the fixing plate.
 10. The siliconcrystallization apparatus of claim 9, wherein, when the substrate isloaded, the adsorption pins project above the fixing plate so as to fixthe substrate, and then the fixing plate is moved down while fixing thesubstrate, so that the substrate is loaded on the surface of the fixingplate.
 11. The silicon crystallization apparatus of claim 9, wherein,when the substrate is unloaded, the adsorption pins project above thefixing plate, so that the substrate is spaced apart from the fixingplate.
 12. The silicon crystallization apparatus of claim 9, wherein thevacuum groove has a lattice shape.
 13. The silicon crystallizationapparatus of claim 6, wherein the sensing device senses cornercoordinates of the substrate.
 14. The silicon crystallization apparatusof claim 6, wherein the sensing device includes at least first, second,and third sensors.
 15. The silicon crystallization apparatus of claim14, wherein the first and second sensors are positioned to correspondwith the two corner coordinates of the length-side direction of thesubstrate, and the third sensor is positioned to correspond with thecorner coordinates of the width-side direction of the substrate.
 16. Thesilicon crystallization apparatus of claim 14, wherein the first,second, and third sensors comprise CCD cameras.
 17. The siliconcrystallization apparatus of claim 14, wherein the first, second, andthird sensors comprise LD sensors.
 18. A silicon crystallization method,which comprises: providing a silicon crystallization apparatus includingan optical device for generating laser beams, a stage for fixing asubstrate having silicon deposited thereon, for being rotatably andmovably provided with the substrate in a horizontal direction, and asensing device for sensing the position of the substrate; forming anamorphous silicon layer over an entire surface of the substrate definedas a display area and a non-display area; fixing the substrate to thestage; aligning the substrate by sensing the fixed substrate with thesensing device, and moving and/or rotating the stage; forming alignmentkeys on predetermined portions of the non-display area of the substrateby correspondingly placing a mask for formation of alignment key abovethe substrate; and crystallizing the amorphous silicon bycorrespondingly providing a mask for crystallization above thesubstrate.
 19. The silicon crystallization method of claim 18, whereinthe process of aligning the substrate includes: positioning first andsecond sensors to correspond with the corner coordinates of alength-side direction of the substrate, and positioning a third sensorto correspond with corner coordinates of a width-side direction of thesubstrate, according to the size of the substrate; detecting the cornercoordinates of the substrate with the first, second, and third sensors;and moving the stage along the X-axis and the Y-axis directions, and/orrotating the stage, so as to detect the corner coordinates of thesubstrate from all of the first, second, and third sensors.
 20. Thesilicon crystallization method of claim 19, wherein the method of movingthe stage along the X-axis and the Y-axis directions, and of rotatingthe stage, includes: minutely moving the stage along the (+)(−)X-axisdirection so as to sense the corner coordinates of the substrate fromthe third sensor, if the corner coordinates of the substrate aredetected from the first and second sensors, and not detected from thethird sensor; minutely moving the stage along the (+)(−)Y-axis directionso as to sense the corner coordinates of the substrate from the firstand second sensors, if the corner coordinates of the substrate aredetected from the third sensor, and not detected from the first andsecond sensors; and rotating the stage so as to sense the cornercoordinates of the substrate from both the first and second sensors, andmoving the stage along the (+)(−)X-axis direction so as to sense thecorner coordinates of the substrate from the third sensor, if the cornercoordinates are detected from any one of the first and second sensors.21. The silicon crystallization method of claim 18, wherein thealignment key is formed in a shape of ‘

’.
 22. The silicon crystallization method of claim 18, wherein, whenforming the alignment keys, the laser beams irradiates at a first energydensity.
 23. The silicon crystallization method of claim 22, wherein thefirst energy density is set at an intensity suitable for ablating theamorphous silicon layer.
 24. The silicon crystallization method of claim18, wherein, when performing the crystallization process, the laserbeams irradiates at a second energy density.
 25. The siliconcrystallization method of claim 24, wherein the second energy density isdetermined as an intensity to completely melt the amorphous siliconlayer.
 26. The silicon crystallization method of claim 18, wherein theprocess of crystallizing the amorphous silicon layer is performed usinga first step of selectively crystallizing predetermined portions of thedisplay area, and a second step of crystallizing a driving circuit partof the non-display area.
 27. A silicon crystallization method, whichcomprises: providing a silicon crystallization apparatus including anoptical device for generating laser beams, a stage for fixing asubstrate having silicon deposited thereon, and for being rotatably andmovably provided with the substrate in a horizontal direction, and asensing device for determining the position of the substrate; forming anamorphous silicon layer over an entire surface of the substrate definedas a display area and a non-display area; fixing the substrate to thestage; aligning the substrate by sensing the substrate fixed on thestage with the sensing device, and moving and/or rotating the stage;forming alignment keys on predetermined portions of the non-display areaby correspondingly providing a mask for formation of alignment key abovethe substrate; crystallizing the amorphous silicon on predeterminedportions of the display area by correspondingly placing a firstcrystallization mask above the substrate; and crystallizing theamorphous silicon of the non-display area by correspondingly placing asecond crystallization mask above the substrate.
 28. The siliconcrystallization method of claim 27, wherein the process of aligning thesubstrate includes: positioning first and second sensors to correspondwith the corner coordinates of a length-side direction of the substrate,and positioning a third sensor to correspond with the corner coordinatesof a width-side direction of the substrate, according to the size of thesubstrate; detecting the corner coordinates of the substrate with thefirst, second, and third sensors; and moving the stage along the X-axisand the Y-axis directions, and/or rotating the stage, so as to detectthe corner coordinates of the substrate from all of the first, second,and third sensors.
 29. The silicon crystallization method of claim 28,wherein the method of moving the stage along the X-axis and the Y-axisdirections, and of rotating the stage, includes: minutely moving thestage along the (+)(−)X-axis direction so as to sense the cornercoordinates of the substrate from the third sensor, if the cornercoordinates of the substrate are detected from the first and secondsensors, and not detected from the third sensor; minutely moving thestage along the (+)(−)Y-axis direction so as to sense the cornercoordinates of the substrate from the first and second sensors, if thecorner coordinates of the substrate are detected from the third sensor,and not detected from the first and second sensors; and rotating thestage so as to sense the corner coordinates of the substrate from boththe first and second sensors, and moving the stage along the(+)(−)X-axis direction so as to sense the corner coordinates of thesubstrate from the third sensor, if the corner coordinates are detectedfrom any one of the first and second sensors.
 30. The siliconcrystallization method of claim 27, wherein the alignment key has ashape of ‘

’.
 31. The silicon crystallization method of claim 27, wherein, whenforming the alignment keys, the laser beams irradiates at a first energydensity.
 32. The silicon crystallization method of claim 31, wherein thefirst energy density is set at an intensity suitable for ablating theamorphous silicon layer.
 33. The silicon crystallization method of claim27, wherein when performing the crystallization process, the laser beamsirradiates at a second energy density.
 34. The silicon crystallizationmethod of claim 33, wherein the second energy density is set at anintensity of completely melting the amorphous silicon layer.
 35. Thesilicon crystallization method of claim 27, wherein the process ofcrystallizing the amorphous silicon with the first crystallization maskis performed while sensing an interval between the alignment key and thepredetermined portion of the substrate irradiated with the laser beams.36. The silicon crystallization method of claim 27, wherein the firstcrystallization mask comprises an open part and a closed part, and alength and a width in the open part of the first crystallization maskare controlled according to a size of a semiconductor layer in eachpixel.
 37. The silicon crystallization method of claim 27, wherein thefirst crystallization mask includes at least one pattern blockcorresponding to a semiconductor layer part in each pixel.
 38. Thesilicon crystallization method of claim 27, wherein crystallizing theamorphous silicon with the second crystallization mask is performedwhile sensing an interval between the alignment key and thepredetermined portion of the substrate irradiated with the laser beams.